Method for transferring coolant from a loading unit to an air conditioning system

ABSTRACT

Method for transferring coolant fluid from a loading unit/station ( 20 ) to an air conditioning system ( 10 ), via at least one high pressure HP valve ( 7 ) and duct ( 15 ), for the introduction of liquid coolant, and at least one low pressure LP valve ( 8 ) and duct ( 17 ), for the suction and the recovery of the coolant-vapour in the system ( 10 ). It is provided for executing the step of transferring the fluid also maintaining the low pressure circuit branch ( 17 ) open/active, through relative LP valve. Part of the coolant loaded during the transfer step passes through a valve for the expansion of the system and it is suctioned, as vapour, by the station through LP: the net amount that enters into the system is always positive given that there is more loaded coolant with respect to the suctioned coolant.

FIELD OF APPLICATION OF THE INVENTION

The present invention regards a method of maintenance of an air conditioning system and a connection device for the use of the latter. In particular, the present invention finds application in the automobile industry, for example in vehicle repair workshops.

PRIOR ART

The air conditioning systems are subject to leakage of coolant fluid and require periodic reloading. Thus, there arises the need to actuate a cycle for reloading and/or regenerating the system; for this purpose, there were developed devices for the maintenance of air conditioning systems capable of executing the recovery, the recirculation and reloading of the coolant fluid in the system.

TECHNICAL BACKGROUND

An air conditioning system is a closed system, which operates on pressure difference and change of state that the coolant gas is subjected to throughout the circuit. The components in question are:

-   -   the compressor, which suctions and compresses the coolant,         modifying its state and the temperature (from low pressure and         low temperature to high pressure and high temperature); it has         the function of compressing the coolant gas, making it pass from         low temperature and low pressure to high temperature and high         pressure. It is a precision component, whose quality has a major         impact in terms of safety, comfort and energy saving. The         compressor contains rotary parts, and thus should be suitably         lubricated with a specific oil, with characteristics suitable         for the refrigerating circuit;     -   the condenser, which transfers heat to the external air and         condenses the coolant, which thus passes from the gaseous state         to the liquid state; in practice, it is a heat exchanger which         serves to cool and thus liquefy the coolant gas coming from the         compressor; it is mainly formed by ducts (primary exchange         surface) and fins (secondary exchange surface). Usually, in         vehicles it is positioned in the front part, before or beside         the engine radiator. It transfers heat to the environment, given         that its temperature is higher with respect to the one         surrounding it. The air passes through the fin elements of the         condenser and, by subtracting heat, it causes the liquefying of         the refrigerating fluid or coolant;     -   the coolant, which traverses the de-hydrating filter, which         absorbs moisture and withholds impurities (the de-hydrating         filter is placed between the condenser and the expansion valve         and it is traversed by coolant in high pressure liquid state);         the coolant then reaches the expansion valve, where it is         subjected to a drastic pressure and temperature drop;     -   in the evaporator, the coolant once again changes its state,         passing from liquid to gaseous. It absorbs heat and lowers the         temperature of the air introduced into the cabin through the         aeration ducts; the evaporator is also a heat exchanger. It is         conceptually identical to the condenser though having the         opposite function. Inside, the coolant passes from the liquid         state to the gaseous state absorbing heat from the environment.         The air which traverses the fins thereof is cooled and enters         into the cabin through the aeration ducts.

General Operation

During the step of recovery and recirculation, the coolant fluid is taken from the air conditioning system through a rapid connection system connected to a recovery duct. Subsequently, the fluid is purified and accumulated in a deposit tank.

During the reloading step, a vacuum pump arranged downstream of the deposit tank creates a depression which moves the coolant fluid from the tank to the air conditioning system.

There can be provided for methods for measuring the mass associated to the tank, so as to monitor both the amount of re-circulated coolant fluid and the amount subsequently injected in the air conditioning system.

In any case, the coolant fluid is subsequently injected in the air conditioning system, generally passing through a quick connection interposed between the loading duct and the coupling on the vehicle side.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a method for transferring coolant fluid from a loading unit or station to an air conditioning system, providing for performing the transfer or loading of the coolant maintaining both high pressure and low pressure branches active, the latter usually dedicated to the recovery of coolant-vapour during emptying of the system.

Advantages:

-   -   it guarantees the completion of the loading in any situation     -   it eliminates the so-called heating bundle used for supporting         the coolant tank, and the duration of the vacuum phase (during         which the bundle is activated) is no longer significant     -   it avoids having to utilize the overheating of the cylinder         which facilitates the loading but slows the subsequent recovery,     -   it offers performance comparable to a good liquid pump (1000         g/min average).

In addition, with a suitable choice of times and regulations of the reloading station, as well as the capacity (flow rate) of the station compressor, it is also possible to reload without performing the vacuum phase, though minimum, and even reload the systems already partly loaded with coolant.

Another object of the invention is to provide a more accurate method so that a precise and well-defined transferring coolant is delivered to the air conditioning system from the tank of the loading unit/station. For this reason an amount of coolant QC greater than the nominal value NA theoretically required is sent to the air conditioning system; afterward said amount in excess is suctioned by the branch of the LP valve and measured. During the recovery phase, a high accuracy can be maintained because this phase is not affected by the uncertainty due to the refrigerant which remains in the liquid phase into the tubes. In fact, during the suction phase, the refrigerant evaporates, and only a negligible amount of refrigerant in vapour form remains in the pipes.

These objects and advantages are attained by the method for transferring the coolant from a loading unit to an air conditioning system, subject of the present invention, which is characterized by what is provided for in the claims below.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other characteristics shall be more apparent from the following description of some embodiments illustrated, purely by way of non-limiting example, in the attached drawings.

FIG. 1: illustrates the operating principle of the method for loading the coolant from the station to the vehicle, of the known type,

FIG. 2: illustrates the operating principle of the method for loading coolant from the station to the vehicle, subject of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

With particular reference to FIG. 1 there is indicated a method for transferring the coolant fluid, of the known type.

For example, reference is made to an automobile vehicle system.

Usually, the method can be actuated after the connection of the air conditioning system to be loaded, in the example indicated in its entirety with reference 10, with at least one unit 20 for the recovery and/or reload of coolant fluid, generally known as “air conditioning station”.

The air conditioning system, which substantially performs a refrigerating cycle, is indicated with:

-   -   a compressor 4;     -   a condenser 2 and ventilation system 1;     -   at least one de-hydrator filter 3,     -   an expansion valve 5;     -   an evaporator 6.

The components described above are connected by a closed circuit schematically illustrated by lines 9; there is also present a low pressure (LP) point of drawing 7 and a point of introduction 8 on the high pressure HP branch; the latter two allow the coupling with corresponding connection devices of an air conditioning station, as described hereinafter, with the aim of performing the maintenance, reload operations, etc. . . .

The air conditioning station, 20, comprises therein:

-   -   a coolant tank 11, or cylinder     -   a cut off valve 12 for opening and closing at least one duct 13         for the exit of coolant fluid, said duct 13 reaches, through         known suitable systems, a     -   HP connection, i.e. at high pressure, indicated with 14         connectable in the relative high pressure HP branch 15 to the         air conditioning system 10, so as to be connected with the high         pressure liquid coolant, or fitting/valve 8;     -   there is also present an LP connection, i.e. with low pressure,         which can be identified with 16, and which can be connected         through the relative branch 17 to the air conditioning system,         in the fitting indicated with 7 generally arranged after the         expansion valve 5; the coolant is in the gaseous state and with         low pressure;     -   A suctioning group 18 which, through special compressor means,         draws/extracts the coolant from the air conditioning system of         the vehicle, through the low pressure branch 17, and takes it         into the tank 11, by means of ducts 19, so as to empty the         system.

Thus, it is usually provided for drawing/recovering the coolant through the branch 17 connected to the low pressure valve, indicated with LP, and reloading, i.e. sending the new coolant, the system through the duct 15 of the valve HP.

In practice the method of maintenance of an air conditioning system, comprises the steps of:

-   -   recovery of the coolant fluid present in the air conditioning         system, on the LP valve side;     -   filtering of the recovered coolant fluid;     -   injection of coolant fluid in the air conditioning system, on         the HP valve side;

By implementing the conventional loading method, i.e. from the air conditioning station to the vehicle, the coolant is transferred passing it from the tank to the system through the HP path, as indicated in FIG. 1.

The method for transferring coolant from the unit 20 to the system 10, subject of the present invention, provides for transferring the fluid from the tank 11 through the duct 13, 15 entering in 8 in the system 10; in addition, it also provides for that the recovery circuit remains active, i.e. open, during said transfer, as illustrated in FIG. 2, identified by the drawing point 7, duct 17 and branch 19 thus allowing the passage of fluid in the circuit through the air conditioning station.

Thus, the low pressure circuit (vehicle side) has a lower pressure than that it would have with a conventional loading: the loaded coolant passes through the valve for the expansion of the system but, given that the LP circuit is open, part of the loaded coolant is constantly suctioned (it is a vapour) by the station through the LP valve and line.

The compressor of the station, recovering the coolant from LP and pushing it into the cylinder, contributes to keeping loading pressure high.

As mentioned previously:

-   -   vapour is recovered from the LP line     -   liquid is loaded from the HP line

Thus, the net amount that enters into the system is always positive, i.e. there is more loaded coolant with respect to the suctioned coolant.

Below is a summary of the advantages that can be obtained with the described and claimed loading method:

-   -   The loading occurs at speeds comparable with those that can be         obtained with a loading gear pump,     -   The loading is always completed automatically, even when the         station is used for loading a system with brief vacuum phase,     -   The recovery from the branch of the low pressure LP valve cools         the system, thus further facilitating the loading.

With suitable choice of the times and adjustment of the loading station, as well as the capacity (flow rate) of the compressor of the station, it loads without performing any vacuum phase, though minimum, and reloads systems already partly full of coolant.

The method for transferring coolant fluid from a tank (11) of a loading unit/station (20) to an air conditioning system (10), said air conditioning station (20) comprising:

-   -   a. a coolant tank (11),     -   b. a cut off valve (12) for opening and closing at least one         duct (13) for the exit of coolant fluid,     -   c. an HP high pressure connection (14) connectable in the         relative high pressure HP branch (15) to the air conditioning         system (10), so as to be connected with the high pressure liquid         coolant, or fitting/valve (8);     -   d. an LP low pressure connection (16) and which can be connected         through the relative branch (17) to the air conditioning system         (10), by means of a fitting/valve (7), arranged after the         expansion valve (5) of the air conditioning system (10);     -   e. a suctioning group (18) which, through compressor means,         draws/extracts the coolant from the air conditioning system         (10), through the low pressure branch (17), and takes it into         the tank (11), by means of ducts (19), so as to empty the         system;         wherein for executing the step of transferring the fluid also         maintaining the low pressure circuit branch (17) open/active,         through relative low pressure LP valve; the activation/opening         of the low pressure LP branch which connects the air         conditioning station to the LP valve of the air conditioning         system, occurs at least partly simultaneously with the         activation/opening of the high pressure HP branch which connects         the air conditioning station to the HP valve of the air         conditioning system.

The part of the coolant loaded during said transfer step passes through the valve (5) for the expansion of the system and it is suctioned, as vapour, by the station through LP so that the net amount that enters into the system is always positive and there is more loaded coolant with respect to the suctioned coolant.

Typically the internal volume range of an air conditioning system 10 of a vehicle is around 1.5 and 2 litres, and requires 400-900 grams of coolant. The expansion valve 5 generates on the LP low pressure branch a pressure of 2-3 bar. For providing the claimed method the compressor of the suctioning group 18 must generates a flow of 25-60 litres per minute.

In the following, there is described a method for transferring coolant fluid from a tank 11 of a loading unit/station 20 to an air conditioning system 10 that guarantees the maximum precision of fluid coolant loaded.

Specifically, the method inserts an amount of coolant QC greater than the nominal value NA theoretically required by the air conditioning system 10, and afterward said amount in excess is suctioned by the branch of LP valve and measured. During the recovery phase, a high accuracy can be maintained because this phase is not affected by the uncertainty due to the refrigerant which remains in the liquid phase into the tubes. In fact, during the suction phase, the refrigerant evaporates, and only a negligible amount of refrigerant in vapour form remains in the pipes.

The following steps are applied:

-   -   the refrigerant is loaded in such a quantity, identified as QC,         greater than the nominal amount, identify as NA, to be charged         (without considering dosing errors in charge); said quantity         being measured by weighting the tank 11 both before starting and         during the charge so that when the quantity of coolant QC         greater than the nominal amount NA to be charged is inside the         air conditioning system 10; the step of transferring the fluid         is interrupted by closing the HP valve,     -   the suctioning group 18 which, through compressor means,         continues to work, namely drawing/extracting the coolant from         the air conditioning system 10, through the low pressure branch         17 (even after the closing of the HP valve)     -   during this further suctioning phase, the quantity of fluid         suctioned is measured and the further suctioning phase goes on         until the amount QC-NA of suctioned fluid has returned into the         tank 11.

EXAMPLE

an example of the process is described hereafter.

Suppose a vehicle requires 700 gr of refrigerant; with the present method 800 gr of refrigerant are effectively loaded into the circuit, according to the steps previously described. This quantity is calculated by weighting the tank 11 and monitoring it during the charge.

The above amount (800 gr) of refrigerant may also not be exactly 800 gr, because of a charging error that can be significant (even +/−50 gr), due to the uncertainty about the amount of coolant remaining in the charging hoses and in the liquid phase. In any case, the important thing is that inside the circuit 11 there is more than the required 700 gr.

Afterwards, the recovery process starts; the recovery process is highly accurate, because it is not affected by the uncertainty due to the refrigerant, refrigerant which remains in the liquid phase into the tubes (during suction the refrigerant in fact evaporates, leaving a negligible amount of refrigerant in vapour form in the pipes).

The recovery measures the tank 11 which receives the fluid recovered and it continues up to all the refrigerant's excess previously loaded has been recovered; in the specific example said excess of refrigerant correspond to 100 gr. At the end, there remains effectively 700 gr in the system, with a typical error of 5 gr.

Taking into account what already reported in the previous pages, the process can also be summarized as comprising the following steps:

-   -   a) activating the low pressure side LP valve, so as to execute         the step of transferring the fluid maintaining the low pressure         circuit branch 17 open/active, through the relative low pressure         LP valve during the loading phase (the charge) starts from the         side of the high pressure HP (activation/opening of the high         pressure HP branch which connects the air conditioning station         to the HP valve of the air conditioning system),     -   b) continuing the charge without interruption, because the         suction from the LP side produces the evaporation of refrigerant         in the system with consequent cooling and lowering of pressure,         so that the system 10 is always at a lower pressure than that of         the tank 11 of the loading station 20,     -   c) stopping the loading phase (closing the HP valve) when the         quantity QC of refrigerant loaded is greater than the nominal         amount NA that is to be charged (namely the quantity that must         be actually loaded),     -   e) continuing the recovery phase by the LP low pressure valve;         during said recovery phase from the LP the quantity of         refrigerant recovered and sent to the tank 11 is measured     -   f) continuing the recovery phase until said measured refrigerant         is equal to the excess of refrigerant, namely QC minus NA. 

1. Method for transferring coolant fluid from a tank (11) of a loading unit/station (20) to an air conditioning system (10), said air conditioning station (20) comprising: a. a coolant tank (11), b. a cut off valve (12) for opening and closing at least one duct (13) for the exit of coolant fluid, c. a HP high pressure connection (14) connectable in a relative high pressure HP branch (15) to the air conditioning system (10), so as to be connected with a high pressure liquid coolant, or a fitting/valve (8); d. a LP low pressure connection (16) and which can be connected through a low pressure branch (17) to the air conditioning system (10), by means of a fitting/valve (7), arranged after an expansion valve (5) of the air conditioning system (10); e. a suctioning group (18) which, through compressor means, draws/extracts the coolant from the air conditioning system (10), through the low pressure branch (17), and takes it into the tank (11), by means of ducts (19), so as to empty the system; the method comprising: transferring the fluid maintaining the low pressure circuit branch (17) open/active, through relative low pressure (LP) valve; the activation/opening of the low pressure LP branch which connects the air conditioning station to the LP valve of the air conditioning system, occurring at least partly simultaneously with the activation/opening of the high pressure HP branch which connects the air conditioning station to the HP valve of the air conditioning system; passing part of the coolant loaded during said transferring through the valve (5) for the expansion of the system and suctioning it, as vapour, by the station through (LP) so that the net amount that enters into the system is always positive and more coolant is loaded with respect to the suctioned coolant, recovering and re-introducing in the tank (11) the amount of coolant suctioned through LP, contributing to keeping loading pressure high, the method further comprising: continuing the charge, without interruption, suctioning from the LP side and producing the evaporation of refrigerant in the system with consequent cooling and lowering of pressure, so that the system (10) is always at a lower pressure than that of the tank 11 of the loading station (20), stopping the loading phase when a quantity QC of refrigerant loaded is greater than a nominal amount NA that is to be charged (namely the quantity that must be actually loaded), continuing the recovering by the LP low pressure valve; during said recovering phase, measuring the quantity of refrigerant recovered and sent to the tank 11, continuing said recovering until said measured refrigerant is equal to the excess of refrigerant, namely QC minus NA. 